A US judge has slashed the multi-billion-dollar award for a couple who blamed the glyphosate-based weed-killer Roundup for their cancer.

Judge Winifred Smith of the California Superior Court in Oakland said the initial damages awarded by a jury of US$2 billion ($2.8 billion) were excessive and unconstitutional, cutting the award to less than US$100 million.

The judge's final order will see California couple Alva and Alberta Pilliod receive roughly US$17 million in compensatory and US$69 million in punitive damages.

Bayer AG – the makers of Roundup – has issued a statement saying the judge's decision to slash the award is a step in the right direction, and that it will file an appeal.

“We continue to believe that the verdict and damage awards are not supported by the evidence at trial and conflict with the extensive body of reliable science and conclusions of leading health regulators worldwide that confirms glyphosate-based herbicides can be used safely and that glyphosate is not carcinogenic,” the company said.

Bayer still faces Roundup cancer lawsuits from more than 13,400 plaintiffs across the United States.

Bayer has already lost three US jury trials over Roundup, with juries in California awarding multi-million-dollar awards. The company is appealing all the decisions.